Driver circuit



J. L. MEDOFF DRIVER CIRCUIT Aug. 26, 1958 Filed Feb. 15, 1956 s H m 0 A T EVEN TARGETS EVEN GRIDS SET=1 RESET=O INVENTOR.

JOSEPH L. MEDOFF E D O m A C ATTORNEY United States Patent Ofifice 2,849,654 Patented Aug. 26, 1958 DRIVER CIRCUIT Joseph L. Medoit, Merion Station, Pa., assignor to Burroughs Corporation, Detroit, Mich., a corporation of Michigan Application February 15, 1956, Serial No. 565,741

8 Claims. (Cl. 315-846) This invention relates to driver circuits and more particularly relates to a driver providing successive switching signals to alternate switching circuits of devices requiring an alternation of switching impulses, such as a magnetron beam switching tube or flip-flop circuits.

The magnetron beam switching tube is a multiposition tube of the magnetron type described in the United States Patent No. 2,721,955, issued to Sin-Pih Fan and Saul Kuchinsky .on October 25, 1955. A magnetron beam switching tube of this type may comprise a cathode with a plurality of beam receiving compartments positioned concentrically in a circular row about the cathode. Each of the compartments comprises a spade electrode for locking the beam in position, a target electrode for receiving the beam, and a switching electrode for stepping the beam from one position to another. The spade electrodes are positioned concentrically about the cathode and spaced apart from each other to permit two adjacent spades to define the side walls of a beam receiving compartment. The target electrodes are arranged concentrically about the spade electrodes and are positioned to individually extend across the spacings between adjacent ones of said spade electrodes to thereby receive substantially the entire beam passing into the compartment. The switching electrodes are arranged concentrically about the cathode and each switching electrode is individually positioned in a separate compartment in .the vicinity of one of the two spade electrodes and the target electrode. A magnetic field is caused .to permeate the tube with flux lines substantially parallel to the cathode and the electrodes. As well known in the art, this magnetic field in conjunction with the electric field set up between the cathode and target electrodes will cause the electron beam to follow a path extending between two spades when all spades except one are at a high potential and the one is at about the cathode potential. As the beam enters the compartment adjacent to the low potential spade on the side from which electrons are coming, part of it will be received by the low potential spade and will develop an IR voltage drop in a series connected resistor to hold its potential at a low value and keep the beam locked in on the target electrode.

To provide switching of the beam .to the next compartment, the switching electrode is so positioned .as to alter the beam path so that the adjacent high potential spade receives beam current. This lowers the potential of .the spade enough to cause the .beam to step into the adjacent compartment. The beam normally progresses from one compartment to the next in that directiondefined by the polarity of the'magnetic field. The electrons travel around the cathode in a direction determined by the application of the right hand-rule for interaction of current and magnetic flux, and the beam advances in the upstream direction on this electron travel. By coupling the switching electrodes into two sets, each including alternate electrodes, the electron beam can be caused to advance from one compartment to the next by changing the potential of the two sets of switching electrodes alternately.

To switch the beam of magnetic beam switching tube, all grids can be in one common connection and driven to switching potential only for a closely quantized interval; long enough for the beam to switch one position but not long enough for two positions. The shaping of such a pulse requires comparatively elaborate circuitry.

Another method of switching is to connect the grids in two common-circuits of alternate grids, called the odd and the even grids. An alternating Voltage of switching amolitude then is applied between these common circuits. As one set of grids goes negative, the other set goes positive. Thus, when a negative swing causes .a beam switch from one position the grid of the next position is swinging positive which prevents a second switch ing step on one pulse. Only on the next half cycle can the next switching step occur. This method requires either a balanced, push-pull, input signal or flip-flop circuitry for deriving push-pull signals from a single ended input signal.

An object of this invention is to provide a driver circuit responsive to randomly occurring, single-ended input pulses to provide successive switching pulses alternately to apair of switching circuits.

Another object of this invention is to provide a magnetic cored driver for magnetron beam switching tubes, responsive to single-polarity pulses to provide switching pulses alternately to common circuits of alternate switching grids and in synchronism with the advance of the electron beam, in said tube.

Another object of this invention is to provide a driver for magnetic beam switching tubes having a pair of magnetic cores respectively coupled to alternate sets of targets and switching grids, wherein incoming pulses set the pair of cores to one magnetic condition, a build up of beam current in either set of targets resets the associated core to the other magnetic condition, and either set of alternate switching grids is driven by voltage induced from the associated core, when that core is set to the one magnetic condition, to switch the beam to the next beam holding position.

Reference is made to the drawings in which:

Fig. 1 is a schematic diagram of a magnetic cored driver for a magnetron beam switching tube;

Fig. 2 is the BH curves for magnetic cores of the circuit in Fig. 1; and

Fig. 3 is a sectional view of a coaxial magnetron beam switching tube.

In Fig. 1, portions of a magnetron beam switching tube 20 are shown. Targets 7.1 are connected through load resistors 22 to common circuits of alternate targets, calledrespectively the even (0, 2, 4, 6, 8) and the odd ,(1, 3, f 7, 9) targets. The switching grids 23 also are ,connected in common circuits of alternate grids corresponding to the target circuits, to provide even and .odd circuits. Spade 24' for the initial or 0 position is separately connected through its series resistor 25 to voltage divider resistors 26 and 27. The remaining spades 2,4 are connected through series resistors .25 and common resistor 28 to the voltage supply +E.

The .common circuit for even targets is coupled to magnetic core 313 through winding .32. Similarly, the odd targets are coupled to magnetic core 31 through winding 33. .Both target circuits thenconnect through resistor 28 to voltage supply +E. Both windings 32 and 33 are connected so that a build-up of target current gencrates a magnetizing force H which tends to reseta core to the zero magnetic condition, and cutting oil target current allows the -built-up magnetic field to collapse, thereby facilitating the setting of a core in the one magnetic condition.

The common circuit for even grids is coupled to core 30 through winding 34. Similarly, the odd grids are coupled to core 31 through winding 35. Both grid circuits then connect to bias supply 39. Windings 34 and 35 are connected so that a change in flux from zero condition to one" condition will induce a negative voltage on the switching grid side of these windings. When a position in the tube holds an electron beam, application of the above negative voltage to the grid of that position will cause the beam to switch.

Driver tube 38 has its plate connected to windings 36 and 37, its cathode grounded, and its grid connected to an input terminal 6t and to a cut off bias E through resistor 61. Switching pulses from tube 38 are coupled to both magnetic cores. Winding 36 couples current from tube 38 to core 30 and winding 37 couples the same current to core 31 because windings 36 and 3'7 are in series from the plate of tube 38 to voltage supply +E. A positive pulse on the grid of tube 38 produces a negative pulse on the plate. This negative pulse on windings 36 and 37 produces a current and magnetizing force which tends to set both cores in the one magnetic condition. If either core is in the zero condition, this setting action to one condition produces a large change in flux in that core and induces a negative switching voltage on the associated grid-connected winding.

In Fig. 2, the curves of magnetizing force, H, versus flux, B, for cores 30 and 31 are plotted. For a magnetic force to the left on the H axis and at or in excess of value H the cores will have a flux B and the condition of the cores can be portrayed as being at points 59 on their BH curves. When the force H is removed, most of the flux will be retained and the condition of the cores moves to points 51. The cores are described as having moved from points 50 to 51. When a force H is applied, the cores then move along their 8-H curves and up to point 52, to Where the fiux in the cores is B This change or" flux from B, to B is a comparatively large fiux change and induces useful signals in windings on the cores. When force H is removed, the cores move to points 53, retaining most of their magnetism. Any repeated application of force H will produce insignificant induced voltages since the flux change from point 53 to B is insignificant. However, re-application of force H will move the cores to point 50, resulting in a large but opposite induced voltage on any windings on the cores.

To examine the operation of the circuit of Fig. 1, assume that both cores are in zero position, corresponding to position 51 of Fig. 2 and the tubes 20 and 38 have warmed up to operating condition. Spade 24' will be held down to about /2E by voltage divider resistors 26 and 27, but the remaining spades 24 will be at voltage E. This voltage difierence distorts the interelect'rode electrical field of tube 20 in the vicinity of spade 24 and causes an electron beam to form on the position of tube 20. As beam current flows through resistor 22, winding 32 and resistor 28, an IR voltage drop is produced in resistor 28 which lowers all electrodes connected to its about /zE, their operating voltage. In flowing through Winding 32, this current produces a magnetizing force H in core 30. With core 30 in zero condition at point 51, an insignificant flux change occurs when force H moves core 30 to point 50A. If core 30 had been in one condition at point 53A, there would have been a large flux change in the move to point 50A, but the induced voltage on winding 34 would put a positive potential on the even grids and no switching would result. Thus, beam formation does not upset initial beam position, regardless of core 30s zero or one condition.

When a switching pulse is applied to tube 38, it drives switching current through windings 36 and 37. This switching current through winding 36 produces a magnetic force which overcomes the force H which beam current through winding 32 produces, and develops a magnetic force H This change in applied magnetic force takes the condition of core 30 from point 50A through 51A to point 52A. The large flux change from B to B induces a negative, grid-switching voltage in winding 34. This grid-switching voltage switches the newly formed beam to the 1. position. As the beam moves away from the zero position target, beam current through winding 32 cuts off and the magnetic field it has produced collapses. Collapse of this field accelerates the setting of coil 30 to one condition at point 52A. When the switching current in winding 36 ceases, core 30 goes to point 53A.

This switching current through winding 37 produces a magnetic force H which moves the condition of core 31 from point 51B, to point 52B. This large flux change from near B to B induces a negative switching voltage on winding 35. However, the beam is not in any of the odd positions when this occurs so a negative switching voltage on odd grids has no results at this time. If core 31 had been in the one condition at point 533, the switching pulses magnetizing force would have moved core 31 out to point 528 and back to point 53B, which produces insignificant flux change or induced voltage.

However, an additional magnetizing force affects core 31 as soon as the beam of tube 20 hits the one position target. Beam current through winding 33 produces magnetizing force H which moves the condition of core 31 from point 533 to point 508 in the zero condition. This large fiux change from B to B induces a large positive voltage on the odd grids, but no switching can result from this positive voltage. In fact, this positive voltage prevents any unwanted switching at this time.

Thus, the first switching pulse from tube 38 after a beam forms on 0 position will switch the beam to the 1 position and inhibit any additional unwanted switching on this single switching pulse. Core 30 is left in the one condition at point 53A, core 31 is left in the zero condition at poi't 50B. Core 31 remains at 50B rather than 5113 because beam current continues to flow through winding 33 and to produce magnetic force H When the next switching pulse is applied and switching current flows through windings 36 and 37, the condition of core 30 goes from 53A to 52A and returns to 53A. This induces little or no voltage in winding 34 due to insignificant flux change. However, core 31 goes from 50B through 51 and 52B to 53B. This large fiux change from B to B again induces a negative switching voltage on winding 35, and this time the beam is switched because it was held in 1 position of the tube where it can be affected by switching voltage on an odd grid. The removal of beam current from an odd target and from winding 33 accelerates this setting of core 31 to one condition at point 53B.

When the switched beam strikes 2 position target,

beam current fiows through winding 32 and produces magnetic force H which moves the condition of core 30 from point 53A to point 50A. This large flux change from near B to B induces a large positive voltage on winding 34 and even grids, which inhibits further switching on a single pulse applied to tube 38. Thus core 30 is returned to zero condition and core 31 is returned to one condition by this second switching pulse.

' This switching of the beam one position for every incoming pulse continues as long as the tube 20 is energized. If the beam is momentarily cut ofi, a new beam forms on 0 position due to the voltage difference between spade 24' and all other spades when no beam current flows, and the switching process starts again on the next input pulse. This switching can occur at a random rate and up to high recurrence rates.

This magnetic core driver also can be used on a conventional Eccles-Jo-rdan type flip-flop. Driver tube 38 and windings 36 and 37 would remain coupled as in Fig. 1. Windings 32 and 33 would be cross-connected to the plates of the flip-flop, i. e. the first core would be coupled to the second plate and the second core would be coupled to the first plate. Polarity would remain as shown. Windings 34 and 35 would couple the first core to first grid and the second core to second grid, but would be reversed in polarity to apply positive pulses to these control grids.

When the first tube is conducting, the second core is held at point 50 and thefirst core is set to point 53 of Fig. 2. A switching pulse results in a positive impulse being applied to the grid of the second tube, starting it to conduct, and conventional flip-flop action proceeds. Plate current from the second tube drives the first core to reset or zero condition and on to point 50. This magnetic flux change induces a negative voltage on the grid coupling winding which biases the first tube toward cutolf. This trend comes to a stable halt when the second tube draws saturation plate current and the first tube cuts off.

A highly reliable flip-flop circuit thus is provided by combination of this magnetic cored driver and a flip-flop circuit.

While this driver circuit has been shown and described in combination with a coaxial magnetron beam switching tube as shown in Fig. 3, it is broadly useful with devices utilizing electron current, where a transfer of conductive condition from one position to the next operates on the associated magnetic cores to control or drive the devices in their switching action. The tube of Fig. 3 was selected for description as a typical and very useful embodiment. The concentric arrays of spades, switching grids and targets provide a succession of beam holding positions to which the driver is readily connected and causes a beam to advance in a reliable manner.

What is claimed is:

l. A driver circuit including a magnetron beam switching tube having a plurality of output electrodes and a plurality of switching grids, a pair of saturable magnetic cores, a first winding on each of said cores connected to respective sets of alternate output electrodes of said tube, a second winding on each of said cores connected to respective sets of alternate switching grids of said tube in polarity opposite to said first winding, and a third winding on each of said cores in series circuit coupling a common switching pulse current to both cores in polarity opposite to said first winding.

2. A driver circuit including a magnetron beam switching tube having a plurality of output electrodes and a plurality of switching grids, a pair of saturable magnetic cores, a first winding on each of said cores connected to respective sets of alternate output electrodes of said tube, a second winding on each of said cores connected to respective sets of alternate switching grids of said tube in polarity to apply and induced switching signal to said grids, and a third winding on each of said cores in series circuit coupling a common switching pulse current to both cores in polarity opposite to said first winding.

3. A driver circuit comprising, a pair of saturable magnetic cores, a first winding on each of said cores, a second winding on each of said cores, a third winding on each of said cores in series circuit, and a magnetron beam switching tube having a plurality of output electrodes connected to said first windings in respective sets of alternate output electrodes and a plurality of switching grids connected to said second windings in respective sets of alternate switching grids corresponding to the output electrodes which are coupled to the same core and in opposite polarity to the connections of said output electrodes to said first windings.

4. A driver circuit comprising, a pair of saturable magnetic cores, a first winding on each core, a second winding on each core, a third winding on each core and in series circuit, a flip-flop circuit having a pair of output electrodes in a tube envelope cross connected to said first windings and a pair of control grids in said envelope and connected to said second windings respectively on the core coupled to the output electrode controlled by the other grid, and magnetizing means responsive to switching pulses to set said cores in one magnetic condition.

5. A driver circuit including magnetron beam switching tubes having a plurality of targets connected in sets of alternate targets and a plurality of switching grids connected in sets of alternate switching grids, a pair of saturable and highly retentive magnetic cores, a first winding on each of said cores connected in series and responsive to switching pulses to set said cores in one magnetic condition, a second winding on each of said cores connected respectively to one of said sets of alternate targets and responsive to initiation of output current to reset the respective cores to the other magnetic condition, and a third winding on each of said cores connected respectively to one of said sets of alternate switching grids corresponding to the connections to associated sets of alternate targets and responsive to a core changing from said other magnetic condition to said one magnetic condition to produce a switching signal.

6. In a driver circuit for magnetron beam switching tubes a circuit comprising, a saturable magnetic core of high retentivity a tube envelope, a target electrode within said envelope magnetically coupled to said core to set it in a first magnetic condition upon receipt of beam current on said target electrode, a pulse input circuit magnetically coupled to said core to set it in a second magnetic condition upon receipt of an input pulse, and a beam switching control grid within said envelope magnetically coupled to said core to derive a switching signal therefrom upon said core changing from said first to said second magnetic condition.

7. In a driver circuit for electron tubes a circuit comprising a saturable magnetic core of high retentivity an evacuated tube envelope, an output electrode within said envelope and magnetically coupled to said core to reset it in a first magnetic condition upon receipt of beam current on said target electrode, a pulse input circuitmagnetically coupled to said core to set it in a second magnetic condition upon receipt of an input pulse, and a control grid within said envelope magnetically coupled to said core to derive a switching signal therefrom upon said core changing from said first to said second magnetic condition.

8. A driver circuit for electron flip-flop circuits having at least a pair of output electrodes and at least a pair of grids said electrodes and grids being mounted in an evacuated envelope, said driver circuit comprising a pair of saturable and highly retentive magnetic cores, a first winding on each of said cores connected in series and responsive to switching pulses to set said cores in one magnetic condition, a second winding on each of said cores connected respectively to one of said output electrodes and responsive to initiation of output current to reset the respective cores to the other magnetic condition, and a third winding on each of said cores connected respectively to one of said grids corresponding to the connections to associated output electrode and responsive to a core changing from said other magnetic condition to said one magnetic condition to produce a switching signal.

References Cited in the file of this patent UNITED STATES PATENTS 2,254,214 Gage Sept. 2, 1941 2,281,572 Gage May 5, 1942 2,575,370 Townsend Nov. 20, 1951 

